Fluorohydrocarbons by reacting hydrogen fluoride with acetylenic hydrocarbons



Patented Mar. s, 1948 FLUOROHYDROCARBONS BY ACTING. HY- DROGEN FLUORIDEWITH ACETYLENIC HYDROCARBONS Leroy Frank Salisbury, Wilmington, Del.,asslgnor to E. I. du Pont de Nemours & Company,

Wilmingto No Drawing.

11, Del., a corporation of Delaware Application mm 21, m4, slll'lll Is-559,841

This invention relates to the preparatlcndf' Jects will become apparentfrom an examination fluorohydrocarbcns and especially ofvinyl rides.

Many catalysts consistsing of metals and their oxides either alone orsupported on suitable substrates are known to catalyze the reactionbetween acetylene and hydrogen fluoride to-produce vinyl fluoride.Particularly useful compositions are those obtained by impregnatingchar-- coal with a suspension of mercury oxide or by formation of theoxide in situ on the charcoal. In the copending application. of LeroyFrank Salisbury, Ser. No. 508,243, filed October 29, 1943, highly usefulcharcoal-supported mercury compound catalysts are disclosed asemployable in the synthesis of vinyl fluoride from acetylene andhydrogen fluoride. In the copending application of Arthur LivingstonBarney, Ser. No. 517,837, filed January 11, 1943, there are alsodescribed compositions comprising mercury oxide at least partiallycombined chemically with an oxide of nitrogen supported on analkalineearth metal salt. Although these catalysts and especially thosedescribed in the aforementioned applications of Salisbury and Barney areadvantageously useful for their designed purposes, at times theyarecharacterized by certain disadvantages Thus, a large part of thetotal'mercury pre P It on the charcoal may be lost as free mercuryeither during the catalyst preparation or during its operation, thusreducing its activity. These charcoal-sum ported mercury catalysts,although initiallyvery active in the synthesis of vinyl fluoride and.2-fluorobutadiene-l,3, tend to become less active during use, for instancein l2 to 16 hours they may frequently lose as much as 50% of theiroriginal activity. I

It has been found that the above disadvantages may be overcomeefiectivelythrough the employment of certain salts of divalent mercurysup-' ported on charcoal or other carrier.

Accordingly this invention has as an object the provision ofamethod forobtaining fluorohydrocarbons which is not subject to the aforementloneddisadvantages. A further object isthe provision of a practicable processfor obtaining compounds of the general formula RCF= CH: (wherein His ofthe group-consisting 01 hydrogen atoms and monovalent hydrocarbonradicals). A still further object is to provide a new and improvedmethod for obtaining vinyl fluoride from acetylene and hydrogenfluoride; Still another object,

is to provide a new and improved method for preparing2-fluorobutadiene-l,3 from monovinylacetylene and hydrogen fluoride.vAdditional obnew of the following description and claims.

These and other objects and advantages are accomplished according to theherein described invention which broadly comprises passing a mixture ofhydrogen fluoride and a compound having a molecular weight of not morethan and the general formula RC=CH, wherein R is of the group consistingof hydrogen atoms and monovalent hydrocarbon radicals, over a cataylstof the group of mercuric salts consisting, of mercuric acetate, mercuricchloroamide, beta-chloroethenyl mercuric chloride, mercuric phosphateand mercuric sulfide, said mixture being passed over said catalyst undersubstantially anhydrous conditions in thevapor phase ata temperaturewithin the range of from 25 C. to 250 (1., said catalyst being supportedon a carrier.

One preferred embodiment of this invention comprises passing a mixtureof hydrogen fluoride and acetylene in the vapor phase over acharcoalsupported mercuric salt selected from the group consisting ofmercuric acetate, mercuric chloroamide, beta-chloroethenyl mercuricchloride, mercuric phosphate, and mercuric sulfide as a catalyst, saidmixture being passed over said catalyst under anhydrous conditions at atemperature within the range of from 30 C. to 0., the mol ratio ofhydrogen fluoride toacetylene being within the range of from 2/1 to,1/1.

Another preferred embodiment of this invention. comprises passing amixture of hydrogen fluoride and monovinylacetylene in the vapor phaseover a charcoal-supported mercuric salt selected from the groupconsisting of mercuric acetate, mercuric chloroamide, beta chloroethenylmercuric chloride, mercuric phosphateand mercuric sulfide as a catalyst,said mixture being passed over said catalyst under anhydrous conditionsat a temperature within the range of from 30 C. to 100 C. the molratioof hydrogen fluoride to monovinylacetylene being within the rangeof from2/1to1/l. a

The following examples are given for illustrative purposes and are notintended to place any restrictions on the herein describedinvention.

Example I consisting of mercuric'acetate-on-charcoal con-.

tained in a jacketed tubular converter maintained at 40 C. The exitgases are freed of hydrogen fluoride by passage through granulated sodalime, then freed of any moisture by passage through anhydrous calciumchloride, and finally condensed in a trap cooled with solid carbondioxide and acetone. After hours operation, vinyl fluoride is found inan amount corresponding to about an 86% conversion on the basis of theacetylene passed into the reactor. Analysis of the oil gas indicated theproduct to consist of 95.9% vinyl fluoride, 4% acetylene and 0.1% of1,1-difluoroethane.

The catalyst used in the above example is prepared as follows.

Fifty-one and four tenths grams of mercuric acetate are dissolved in 8cc. of glacial acetic acid and the solution made up to 150 cc. withdistilled water. Three hundred cc. of charcoal are impregnated with theabove solution and the mass dried by heating it over a steam bath for 48hours under a water-pump vacuum and then for 20 hours more at 100 C.under an oil-pump vacuum. The finished catalyst analyzes 26.46% mercuryand 0.28% water.

Example II A mixture of dry gases consisting of hydrogen fluoride andacetylene, in which the mol ratio of HF to HC=CH is 1.7/1, is passed ata space velocity of 170 over a mercuric chloroamide-oncharcoal catalystcontained in a converter heated at 40 C. The oil gases are passedthrough soda lime, then through calcium chloride and finally condensedin a. trap cooled with solid carbon dioxide and acetone. Analysis of theproduct, after a 5-hour run, shows a conversion to vinyl fluoride of 61%and the ofi gases are found to contain 92% vinyl fluoride and 8%acetylene.

The catalyst of the above example is prepared by suspending in watergranular charcoal (8-14 mesh) which has been impregnated with 180 g. ofmercuric chloride per liter of charcoal and adding excess aqueousammonia to the suspension. After stirring for several minutes themixture is filtered and washed with water. The moist product is dried at180 C. under a slow stream of dry air, The product analyzes 25.6%mercury, 1.1% nitrogen, and 8.93% chlorine. The atomic ratio .of mercuryto nitrogen is 1/ 1.6.

Example III Example II is duplicated using beta-chloroethenyl mercuricchloride on charcoal as a catalyst. This catalystis obtained byimpregnating charcoal with a benzene solution of chlorovinyl mercuricchloride made by saturating aqueous hydrochloric acid solution withmercuric chloride and treating with acetylene as described in ComptesRendus 26, #1, 60-64. After 6 hours of use the conversion to vinylfluoride is 36%.

A suitable form of apparatus for use in the synthesis offluorohydrocarbons according to the process of this invention consistsof a. reactor, which, for all scale operations, may be constructed froma piece of iron pipe and which contains the catalyst. The reactor may beequipped with an internal temperature measuring device and is preferablyimmersed in a bath of a suitable liquid, e. g., water, so that theinternal temperature may be controlled. The gaseous mixture, aftercontact with the catalyst, passes through an absorbent for the excesshydrogen fluoride, if

any, such as granular soda lime, a drier, and

finally a trap cooled with solid carbon dioxideacetone mixture, Thereaction product which collects in the cold trap is separated into itsindividual components by fractional distillation.

For efllcient operation in the synthesis of 2-fluorobutadiene-1,3 fromhydrogen fluoride and monovinylacetylene, it is essential that thereacting gases must not be allowed to mix until they enter the reactionchamber. If this precaution is not observed, 1. e., if the gases aremixed before they enter the reactor, the reaction between themonovinylacetylene and hydrogen fluoride proceeds as usual but the feedline to the reactor soon becomes plugged with a hard solid Containingless than 10% fluorine, This unwanted reaction is sometimes so rapidthat the run must be stopped and the apparatus dismantled within onehour from the start of the operation; One practical way of overcomingthis serious difilculty is to introduce. the gases into the reactorseparately, e. g., through a T-fltting at the entry of the reactor..This simple device leads to the very unexpected result of completelyeliminating stoppage, which takes place if the gases are mixedbeforehand. The gases can, however, be mixed before they come in contactwith. the catalyst, provided this is done over a granular material suchas charcoal. For example, the T-fitting at the entry end of the reactormay be, and preferably is, filled with dry, granulated, charcoal or'with the catalyst itself. In practice, anhydrous hydrogen fluoride ismetered and led to one end of the T-fitting, and the an hydrousacetylene is also metered and led to the other end of the fitting, .Aninert gas such as nitrogen may be mixed with either the hydrogenfluoride or the acetylene, if desired.

While a form of apparatus suitable for use on a small scale has beendescribed, the operation may be conducted successfully in anyappropriate apparatus, provided the precautions indicated above areobserved.

It is to be understood that the catalyst must be supported on a carrier.As a carrier for the catalysts used in the practice of this inventioncharcoal derived from the incomplete combustion of animal or vegetablematter, e. g., wood, bones, nut shells, coconut, etc., is preferred onaccount of the superior results had therewith. The active charcoal maybe in granular or in finely divided condition. When used in a finelydivided state, a settling chamber must be attached to the furnace orheating element in order to permit the charcoal to settle out of the gasstream during preparations. Other excellent support-s include magnesiumfluoride and alka line earth metal salts, such as those described incopending application Ser. No. 517,837, filed January 11, 1943, byArthur Livingston Barney, the use of which will be found to promote theactivity, prolong the effectiveness of the catalysts, and reduce mercuryloss during roasting operation.

' It is to be understood, of course, that the only catalysts operable inthe process of this invention, i. e., the only catalysts which result ina process not subject to the aforementioned disadvantages of the priorart processes, are mercuric salts selected from the group consisting ofmercuric acetate, mercuric chloroamide, beta-chloroethenyl mercuricchloride, mercuric phosphate and mercuric sulfide.

Any compound having a molecular weight of not more than and the generalformula RCECH, wherein R is of the group consisting of hydrogen atomsand monovalent hydrocarbon radicals may be reacted with hydrogenfluoride in accordance with the process of this invention. One group ofcompounds of the aforementioned general formula which is particularlywell adapted for use in the process of this invention is that roup ofcompounds having a molecular weight of not more than 85 and the generalformula R'CH=CR"C CH, wherein R and R" are selected from the groupconsisting of hydrogen atoms and'monovalent saturated hydrocarbon.radicals. Included among examples of compounds having the formula RCECHas hereinbefore defined are: acetylene, monovinylacetylene,methylacetylene, pe'ntene- 3 yne-l, hexene-3-yne-l, 3 -1methyl-.butene3- yne-l, and the like.

The process of this invention is operative at temperatures within therange of from C. to 250 C. However, optimum results are had when saidprocess is effected at a temperature within the range of from C. to 100C. The

ratio of hydrogen fluoride to the compound atmospheric pressure, butsuperatmospheric.

pressures or subatmospheric pressures may be used if desired. 1

Space velocity may be varied over a wide range and is generally withinthe range of from to 300 because under these conditions optimumconversions are obtained.

By the term space velocity," as employed herein. and in the appendedclaims, is meant the rate at which the gaseous reactants pass throughthe catalyst and is defined as the, number of volumes of gas, calculatedat standard conditions, that traverse one volume of catalyst during onehour.

As many apparently widely different embodiments of this invention may bemade without departing from the spirit and scope thereof, 'it is to beunderstood that I do not limit myself to the specific embodimentsthereof except as defined in the appended claims, I

Having described the present invention, the following is claimed as newand useful:

1. The process for obtaining afluorohydrocarhon, which comprises passinga mixture of hy- 6 drogen fluoride and a hydrocarbon of molecular weightnot greater than 85 having the general formula RCECH, wherein R is ofthe group consisting of hydrogen atoms and monovalent hydrocarbonradicals, over charcoal-supported mercuric acetate as catalyst, saidmixture being passed over said catalyst under substantially anhydrousconditions in the vapor phase at a temperature within the range of from25 C. to 250 C., the mol ratio of hydrogen fluoride to hydrocarbon beingwithin the range of from 3/1 anhydrous conditions at a drogen fluorideand a hydrocarbon of molecular weight not greater than having thegeneral formula RCECH, wherein R is of the group consisting of hydrogenatoms and monovalent hydrocarbon radicals, over charcoal-supportedmercuric acetate, as catalyst, said mixture being passed over saidcatalyst under substantially anhydrous conditions in the vapor phase ata tem- :erature within the range of from. 25 C. to 0 C.

. 2. The process for obtaining a fluorohydrocarbon, which comprisespeeling amixturo of hy- 3. The process for obtaining afluorohydrocarbon, which comprises passing a mixture of hydrogenfluoride and a hydrocarbonof molecular weight not greater than 85 havingthe general formula R'CHZFCRHCECH, wherein R and R are of the groupconsisting of hydrogen atoms and monovalent, saturatedhydrocarbonradicals, over charcoal-supported mercuric acetate, as catalyst, saidmixture being passed over said catalyst under substantially anhydrousconditions in the vapor phase at a temperature within the range of from30 C. to C., the mol ratio of hydrogen fluoride to hydrocarbon beingwithin the range of from 2/1 to 1/1.

4. The process for obtaining vinyl fluoride,

which comprises passing a mixture of hydrogen fluoride and acetyleneover charcoal-supported mercuric acetate, as catalyst, said mixturebeing passed over said. catalyst under substantially temperature withinthe range of from 30 to 100 C., the mol ratio of hydrogen fluoride toacetylene in said mixture being within the range of from 2/1 to 1/1.

5. The process set. forth in claim 4 wherein the gaseous mixture ispassed over the catalyst at a space velocity within the range of from 50to 300.

6. The process for obtaining 2-fluorobuta (Ilene-1,3, which comprisespassing a mixture of 7 hydrogen fluoride and monovinylacetylene overcharcoal-supported mercuric acetate, as catalyst, said mixture beingpassed over said catalyst under substantially anhydrous conditions at atemperature within the range of from 30 C. to 100 C., the mol ratio ofhydrogen fluoride to monovinylacetylene in said mixture being within therange of from 2/1 to 1/1,

LEROY FRANK SALISBURY.

REFERENCES CITED The following references are of record in the flle ofthis patent:

UNITED STATES PATENTS Number Name Date- OTHER REFERENCES Soil i- May a1,1938

